For somebody who doesn't ride a lot, wants an easy-to-start bike, and won't be going fast, on an upright townie, 42x16 is way too tall, let alone 45x16. Like, if you don't think it's way too low, it's probably too high for your friend.
I'd go 42x20 to start with, or 45x21. 45x21 is 2% higher than 42x20, both work out to around 13 mph at 80 rpm. 45x20 gets you to 14 mph at 80 rpm, and is as high as I would go.
My bike is set up with a 1x6, 42 x 14, 16, 18, 20, 23, 26. I spend most of my time in the 20 and the 18, depending on the wind. (When I add a 45t outer ring for half-step, the 45x20 will split the 42x20 and 42x18... I bet I'll be in it a lot.)
--Shannon